As is well known, a rotary press contains a plurality of upper and lower punches, which are guided in suitable guide bores of punch guidings and which co-operate with bores in a die plate. The individual punches feature a shaft, as well as a head at one end, which co-operates with compression rollers of the press. At the end turned away from the punch head is arranged a punch insert, which is realised separately and adapted to be connected with the shaft via suitable fastening means. The connection takes place with the aid of screws or pins. However, it is also known to realise compression punches in one single piece.
The known punch constructions have several disadvantages. Installation and disassembly of the punch inserts is sumptuous, and time-consuming in particular. Replacement of the punch inserts is not possible within the rotary press. The fastening of the punch inserts is susceptible to troubles and subject to high wear. Problems arise also with respect to the centring and alignment of the punch inserts, with compression moulds that are not round in particular. Finally, even the aptitude for cleaning of the known compression punches is bad, in particular if they must remain in the press (CIP=Cleaning in Place). A reason is the existence of threads, corners and seams.
The present invention is therefore based on the objective to provide a compression punch for a rotary press which ensures uncomplicated installation and disassembly of the punch insert and which permits cleaning inside the press.